Paul,
I tested several different connection configurations/materials:
Compressed SCAT duct, strected out SCAT duct, SCEET, which is smooth on
the inside, and finally a thin walled silicone tube.  I was not able to
measure any difference between the options in terms of flow.  What
turned out to have a significant impact was ensuring a positive seal on
both ends of the duct.  The other noteworthy observation was the
difference in vibration passed from the engine to the cowl.  Anything
with resistance in shear passed on more vibration.  SCAT duct is indeed
very lossy on a per unit length basis.  Given the short length of less
than an inch this became a second order issue.  Indeed, efficiency and
drag were foremost on my mind.
Chris




Chris Zavatson
N91CZ
360std
www.N91CZ.com


Christopher Zavatson
BAE Systems
(408)289-4329